Spherical pellet delay device



Feb. 14, 1961 E. BURRELI, 2,971,463

SPHERICAL PELLET DELAY DEVICE Filed July 30, 1951 2 Sheets-Sheet 1 mmmmillmm L Nl llllh ELL/5 BURRELL BY /m Y INVENTOR Feb. 14, 1961 E. BURRELL 2,97,463

SPl-IEIR-IC'AL PELLETDELAY DEVICE Filed July 30, 1951 2 Sheets-Sheet 2 FIG. 5

INVENTOR ELL/5 BURRELL BY jg@ @QM Q5/5MM ATTORNEY SPMRICAL PELLET DELAY DEVICE Ellis Burrell, Rochester, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed July so, 1951, ser. No. 239,286 2 claims. (ci. 1oz-70.2)

This invention relates to time delay devices and in particular to such devices that -must be low in cost, simple in construction and, in particular, positive and accurate in providing the desired delay interval. Although applicable in many arts, the timing device of the invention may be employed to particular advantage in artillery projectiles of the type which rotate at high vspeeds when fired from a gun, and, therefore the invention will be described in a form suitable for this use, although it will be understood that the invention may be used for other purposes as well.

Arming safety devices for electrical artillery fuzes heretofore commonly utilized either a mercury switch or a clock-type switch to maintain a short circuit across the electrically-detonated primer, or squib. To assure the safety of gun crew personnel, such arming devices must be absolutely positive in operation and accurate in maintaining the short circuit until the projectile is well away from the gun. Clock type switches are sufficiently positive and accurate but are exceptionally expensive to manufacture. Mercury spin switches deteriorate after a comparatively short shelf life, particularly when stored under conditions of high temperature and humidity, and consequently are impractical for arming-protection. It is an object of the invention to provide a time delay device that is positive and accurate in operation and yet simple and compact in construction and adapted for manufacture at low cost. It is a further object of the invention to provide an improved arming safety device that is accurate and positive in operation, capable of withstanding the forces imparted to a projectile during the firing thereof, and uniniiuenced by storage for long periods of time under conditions of high humidity and temperature. An object of the preferred embodiment of the invention is to provide such a safety device which is adapted to positively maintain a Short circuit across an electrical element until a desired interval after a projectile containing the delay deviceis fired.

It is a further object of the invention to provide a delay mechanism for use in rotating projectiles which remains inoperative except when influenced by both setback and centrifugal force. It is an object of the preferred embodiment of the invention to provide such a delay mechanism which is adapted to normally shortcircuit an electric element and to remove the short circuit in response to the inuence of both setback and centrifugal force a predetermined interval after the projectile is fired.

It is an object of an alternative embodiment of the invention to provide a delay device which is adapted to sequentially perform a plurality of switching operations after different time delays. It is also an object of this alternative embodiment of the invention to provide a delay mechanism which is adapted to normally vshortcircuit a plurality of electrical elements and to remove the short circuits sequentially after different time delays in response to the inuence of both setback and of centrifugal force. According to the invention,a'multip1icity of spherical 2971A@ Patented Feb. 14, 1961 pellets are disposed within a container having a normally' closed orifice, and means are provided to normally maintain pressure against the pellets tending to force thern` through the orifice. Means are provided to open the orifice at the start of the desired delay interval and to continually clear the ejected pellets from in front of the' orifice. Means adapted to accomplish the desired switching is actuated after a predetermined number of pellets, corresponding to the desired time delay, have' been forced through the orifice.

ln the preferred embodiment of the invention, a multiplicity of spherical glass pellets are maintained under pressure within a cylinder by a spring-urged piston. A thin, frangible, metallic shorting strip normally adapted to short-circuit an electrical element is stretched taut in front of, and adapted to be broken after a predetermined travel of the piston. An orifice leading from the cylinder is normally closed by a pivoted member which `is springurged in an inoperative position and adapted when rotated outward under the inuence of centrifugal force to open the orifice. The piston which causes the shorting strip to be broken is thus normally retained in a safe position by the glass spherical pellets that are confined in the cylinder above the piston. Av setback pin normally prevents outward movement of the pivoted member until a projectile containing the delay mechanism of the preferred embodiment of the invention is fired. After the setback pin moves out of its path, the pivoted member rotates outward under the infiuence of centrifugal force and opens the orifice, allowing the spherical pellets to be forced out of the cylinder into a reservoir. Centrifugal force continually clears .the ejected pellets from in front of the orifice. As the glass pellets escape, the springurged piston travels further into the cylinder until the shorting strip is broken. The distance normally separating the piston and the shorting strip determines the piston travel required to break the shorting strip, and thus the number of spherical pellets that must be ejected through the orifice to accomplish the desired delay.

In the alternative embodiment of the invention adapted to accomplish two different unshorting operations after different time delays, a rotatable gate containing both a detonator and an unshorting pin is normally detented in an unarmed position by a rod connected to the pelletdelayed piston. A wire to be broken by the unshorting pin is stretched taut in the path of rotation of the pin. A frangible unshorting strip is stretched taut in front of a breaker point located in the top of the piston, As described for the preferred embodiment of the invention, setback and centrifugal force causes the pivoted member to rotate and open the orifice. After the removal of a predetermined quantity of pellets from the cylinder, the rod is removed from its detented position in the gate permitting it to rotate under the influence of centrifugal force, The rotation of the gate allows the unshorting pin to shear the taut wire and thus accomplish the rst unshorting, and, in addition, aligns the detonator with the remainder of the powder train. The second unshorting is accomplished by the rupture of thefrangible strip by the breaker point after the removal of an additional quantity of pellets from the cylinder.

These and other objects of the invention may be better understood by reference to the accompanying drawings,

' line 4-4 of Fig. 1;

Fig 5 is similar toFigf4 but shows'the position of' j the setback pin after the projectile is tired;

Fig. 6 is a perspective view showing an alternative embodiment ofthe invention.

The time delay v device of the invention may. be employed to particular advantage in artillerypr'ojectiles of the type which rotate at high angular velocities when fired from a gun, 'and lthe cylindrical time delay device l10 `of the preferred embodiment of the invention shown sonnel until the p rojectileis well away from the gun.

The delay device 10 is adapted 'to fit within the tubular sleeve portion of aY radio fuze and to arm the fuze by removing this short circuit a predetermined interval after the projectile is fired. Three coaxial insulating discs of equal diameter including a base 11, a cylinder block 12, and a top plate 1e are held integral by screws 15. A radial compartment y16 orthogonal to the axis of Vthe base 11 is adapted to receive an electrically-operated `detonating primer 17, and registering apertures 18, 19 and 26 are provided in the base 11, the cylinder block 12, and the top platelrespectively to receive electrical leads from the detonatlng'squib 17. A primer plug 21 fastened to the base 11seals the squib 17 securely within the compartment 16. An axial opening 22 is provided in the base 11 toallow'the force of'detonation of the squib L17 to be` delivered rearwardly toan auxiliary detonator (not shown) which Ais disposed behind the delay device 10 within the radio fuze. The wires from the detonating primer 17 ,are insulated throughout their length and secured at their extremities to a pair of terminals 24 and 25 which are mount^d in spaced-apart positions in a recess 27 in the front face of the top plate 14. A thin unshorting link 3@ of brass or other conducting material is secured at its opposite ends to the terminals 24 and A2S to normally maintain a shortl circuit across the detonating primer 17. The unshorting link 3l) narrows at its center to a frangible neck portion 31.

A cylindrical axial'compartment 33 provided in the cylinder block 12 is adapted to snugly receive a metallic tubular member 34 to forma piston chamber, or'cylim der 35, containing a multiplicity-of minute spherical glass pellets 37. A piston itl is ladapted to fit snugly/'within the tubular member 34. VThe minutenessof the spherical pellets 37 necessitates a smooth cylinderwalla'nda close tit between the piston itlvand the cylinder 35. Inorder to provide the most accurate timing and to prevent any possibility ofthe minute pellets l37 Vfr'orn'being jammed between the piston il@ and tool marks on the cylinder wall, it is desirable to use a tubular member 3410ii drawn brass in cooperation'with 4a brass piston dit( A bowled, rectangular, metallic spring 41 fitting within'a rectangular recess 42 in` thebase 11 abuts` against/a depending 'axial rod 44 on the piston., TheY spring`,41 urges the piston 40 into the cylinder 35 and'thusmaintins thespherical pellets 37 under pressure within Vthe confined space of the cylinder 35. An axial shaft 46 on the piston'f! extending lupward through the pellets V37 and through an aperture 47` in the cylinder block.12 is provided with vabreaker point 49 of suitable material, such as hard rubberL'which can be easily sheared by manual means, Axially'up'ward Vmovement o f the piston 4 0 with' theshaft-extending into an openingSl in the top .plate 1 4 causes the breaker point 49 to abut against and eventually shear the `unshqrting link 30 at the frangible neck portion 31 1n' the preferred embodiment of thes'inyentio;this.unshorting link v30cc msists of'a'stripof springbrass .0025.inch thick by f V ".'0'15 inch wide at the narrow neck portion 31'.A The piston v Y4 40 is normally retained in a safe, i.e., inoperative, position by the spherical pellets 37 confined in the cylinder 35 above the piston 40. The unshorting link 30 remains intact and maintains a short circuit across the detonating squib 17 until it is broken by the breaker point 49.

An orifice 54 leading from the cylinder 35 through the wall of the tubular member 34 and into a reservoir S5 in the cylinder block 12 isnormally obstructed by a valve 57 fitting and rotatable within a cylindrical aperture58 in the cylinder block 12. A weighted valve arm 60 secured to the upper end of the valve 57 is disposed within a recess 62 in the top plate 14. The ends-of a torsion spring 63 looped aroundl an extension of the valve 57 within a slot 64 in the valve arm 60 abut against the valve arm and against a vertical wall of the recess 62 to urge the valve arm 6th inward. The valve assembly including the integral valve arm 60 and valve 57 is thus normally held in a closed position by the torsion spring 63. An orifice V65 provided in the valve 57 is brought into registry with the orifice 54 when the valve assembly is rotated outward against the forces in the torsion spring 63 by the infuence'of centrifugal force acting on the valve arrn 6) to position the Vvalve arm 60 against the outer wall of the recess 62. The oriiice 65 in the'valve 57 in vregistrywith theorice 54 provides an outlet for the `spherical pellets 37 retained under( pressure within the -cylinder 35. Y Y `As shown in the enlarged sectional view of Fig. 4, the shaft Yof a headed setback pin 71 normally protrudes through4 an aperture 72 in the'cylinder block 12 and into 4an opening 73 in the valve arm 60 to lock the valve as- "sembly against outward rotation if a fuze is dropped or jolted. The aperture 72 widens abruptly into a cylindri- 4calcorr'lpartment 74 which contains the head of the pin 71, a headed rocker 75, and ahelical setback spring`76. The shaft 77' of the rocker 75 fits within the helical spring 76 while the conical head thereof abuts againstV the flat head ofthe setback pin 71, urging it upward against the top of the compartment '74, Under the force of setback the pin 71V and rocker'75 arevdriven rearwardly against thecompressiveforces in the setback spring 76 until the entire pin 71 is'within the compartment 74. The head-of ythepin 71 then pivots about the conical head of the rocker 75 as shown'in Fig. 5, causing the shaft 70 to jam against the top of the compartment 74 where Ait is held by the helical Vspring 76 and prevented from again protruding through the aperture 72. rl l`he valve assembly is thus released to rotate outwardly under the' influence of cen- 'trifugal force. However, if a projectile or a fuze is dropped 'or jolt ed, 'the `fo r c e of gravity alone (with centrifugal force being absent) is insufficient to forcethe pin 71' thr oug'h the aperture 72 into the compartment `74,

' thus preventing release ofthe valve arm 60.

'Ille V setback pin 70 detents the valve assembly against outward movement u ntil 'thefuze is fired in the projectile; thetorsion spring 63 resistsputward rotation of the'valve "assembly until acted upon by centrifugal force from the `firiijg'of a projectile Since the valve assembly can move sov lonlyina direction normal to the axis of the delay device, it cannotv beactuated by theY force of setback. Since the setback pin 71' can move only in an axial direction, it

j cannot be actuated by centrifugalfo'rce. iAccoidingly, opening'of the vorifice'leading from the cylinder 35 can Q beY accomplished only by the operation of the ytwo inter- 65 `connected elements 5 7, 60 by the action o f two independent forces.,

` vThe pistnflt] is normally urged into the cylinder 35 Aby the' bowed "spring,41 acting on the rod 44, When a projectile containing Ithedelay deviceof the invention' is fired, the'forceof setback causesV the setback pin 71j to I nove'rearwardly against the force of thehsetback spring Vv 76 .andcentrifugal force rotateswthevalve assembly out- Award againstrthe torque/ ofthe torsion, spring 63. The

`sphericall pellets 37 contained within the pstonjchamber are .tt1en, ej ected outward throughY the' aligned princes 54 and 65 into the reservoir 55 by both the pressure from the piston 40 and by centrifugal force. Centrifugal force continually clears the ejected pellets from in front of the aligned orifices 54 and 65. Removal of the spherical the valve arm 60 has rotated to align the orifice 65 inV the valve 57 with the orifice 54, thereby allowing sufficient Yglass pellets 37 to be ejected into the reservoir 55 to permit the piston 40 to move upward until the frangible link 30 has been sheared by the breaker point 49. The distance between the end of the breaker pin 49 and the frangible neck portion 31 determines the travel of the piston required to break the unshorting link 30. It will be observed that for a given angular velocity any desired time delay can be obtained, even after the spherical pellets 37 are loaded within the cylinder 35, by cutting the breaker point 49 until it is a predetermined distance from the frangible neck portion 31, which predetermined distance regulates the time delay before the unshorting of the detonating electric primer 17. It will be further observed that it is possible to visually inspect the unshorting link 30 to see that it is intact before assembly of a cover plate 80 upon the time delay device of the invention, thus rendering it impossible for the frangible neck portion 31 to become severed until the combination of setback and spin forces act on the valve arm 60.

It is apparent that other means than the rupture of an unshorting strip by a piston may be utilized to accomplish the desired switching after a predetermined quantity of pellets 37 have been ejected from the cylinder 35,'` and the appended claims are intended to cover all such For example, the weight of the ejected modifications. pellets within the reservoir 55 may be utilized to rupture a frangible link or to close an electrical switch.

The time after a projectile is fired that the unshorting link 30 is broken is a function of the angular velocity of the projectile, the travel of the piston 40, and the size of the orifice 54. Utilizing minute spherical glass pellets 37 in the preferred embodiment of the invention, satisfactory timing is obtained with a .100 inch pistonv stroke and a .030 inch diameter orifice to provide arming pro-V tection for the 3/ 50 gun from 350 to 450 feet from the gun. Tests prove that the time delays obtained on repeated test runs on the same unit, as well as identical test runs on a number of similar units, are exceptionally consistent. With constant orifice diameter and piston stroke, accuraterand repeatable time delays ranging from .25 to 2.5 seconds (dependent upon the angular velocity ofthe projectile) are obtainable with the preferred embodiment of the invention.

The pellets 37 are not ejected one at a time from the orifice, Abut a plurality of pellets are forced out of the orificeat the same time. vrTo prevent jammingof the orifices the pellets must be spherical so that they can slide easily over each other; flat, granular, or otherwise irregular particles jam the orifice and the piston and thus prevent the desired switching. In addition, means should be provided to continually clear the ejected pellets from in front of the orifice in order to prevent jamming and thus assure positive operation.

A delay device intended to provide arming protection for gun crew personnel must be accurate and consistent in timing, low in cost, simple in construction and, above all, positive in operation. To provide these properties, the spherical pellets 37 should be uniformly spherical and of constant diameter, very small in diameter, and possess both nonmagnetic and nonrusting properties. Spherical glass beads meet all of these requirements and in addition, are available in large quantities at low cost.

In the preferred embodiment of the inventionthe most consistent resultsv are obtained when glass pellets 37 are utilized which pass a'No. 60 (.0098 inch) sieve 100% and are retained by a No. 70 (.0083 inch) sieve. To assure that the glass pellets 37 are both chemically clean and free of all foreign matter, they are rinsed in acetone and dried at 220 F. for several hours. In the preferred embodiment of the invention, the most consistent timing is obtained if the glass pellets are lubricated with molybdenum sulfide (MOS) by tumbling them with 5.0 mg. of MOS to each gram of pellets. In addition to causing the glass pellets 37 to ow smoothly, the molybdenum sulfide lubricant prevents scoring of the cylinder 35 and excess friction between the close-fitting piston 40 and cylinder 35.

Although accurate timing is obtainable if spherical steel shots are utilized, the preferred embodiment of the invention is intended for use in artillery projectiles which in some localities are stored for long intervals under conditions of high humidity and temperature, and, consequently, the nonrusting property of glass makes it the preferable material. In order to prevent any possible change in timing characteristics due to the effect of moisture or temperature on the glass pellets 37 in passing through the orifices 54 and 65, the time delay mechanism 10 is soldered within a thin metal can (not shown) after evacuating the can and filling it with an inert gas such as nitrogen before hermetically sealing the unit, Electrical connections are made from the deferred action type battery of the fuze to the detonating primer 17 through metallic pins (not shown) sealed by glass to the metallic can. The glass pellets 37 are remarkably strong and perform perfectly satisfactorily under actual high G gun firings. While gl'ass pellets are utilized in the preferred embodiment of the invention, similar time delay units using spherical pellets of other nonmagnetic and rustproof material, le.g., plastic or stainless steel, are entirely satisfactory in operation.

In the preferred embodiment of the invention, a single delay unshorting operation is accomplished through the rupture of a frangible metallic link by a breaker point fastened to a spring-actuated piston. Spherical pellets contained within a cylinder above the piston prevent motion thereof until centrifugal force rotates a weighted arm to open an orifice leading from the cylinder. The number of pellets that must be ejected from the cylinder before the breaker point can rupture the frangible link is variable to provide the desired time delay by control of the size of the valve orifice and of the piston travel and is also a function of the angular velocity of the artillery projectile. In an alternative embodiment of the invention illustrated in Fig. 6, two separate and distinct timing operations are performed'. The second unshorting is accomplished by the rupture of a frangible link by a breaker point 101 located in the top of a piston 102 in a manner as described for the embodiment of Figs. ll to 5. The piston 102 is urged upward by a helical spring 104 contained within a tubular housing 105. The first unshorting operation is accomplished by utilizing anaxial rod 106 connected to the pelletdelayed piston 102 to control the rupture of a wire 107. The rod 106 normally protrudes into an opening 10S in the rim 109 of a rotatable gate 110 containing a detonator 111 and an unshorting'pin 112 to detent the gate in an unarmed position. The wire 107 to be severed by the unshorting pin 112 is looped around lugs 113 and 114 mounted on an unshorter block 115 so as to be stretched taut in the path of rotation of the unshorting pin 112.

After the removal of a predetermined quantity of pellets 37 from the cylinder 35, the rod 106 moves out of its detented position in the opening 103, permitting the gate 110 to rotate outward under the iniiuence of centrifugal force. This rotation of the gate 110 causes the unshorting pin 112 to shear the taut wire 107 and thus accomplish the desired unshorting, and, in addition,per'mits"the detonator 111 to-'be'rotatedfinto alignment with the remainder of therpowdertranl of'the fuze. yThis first unslio'rting, if.e.,"ef'"thewire-107;occurs before therernovalof ,arf'z'idditional-v quantity of spherical pelletsf37 Yfrom theY cylinder 35,-an'd thus at a finite time interval before thel rupture'of thefra'ngible link 100. It is apparent that the 'peculiartiming-characteristics obtained by metering spherical pelletsF from a container can be utilized for ygeneral tirneidelayfpurposes, eg., to perform a sequence of timing operations. A plurality of shafts attached to the piston 102 may, for example, be utilized to normally detent a plurality of centrifugally-operated valves and-tdsequentiallyrelease the valves after differentpredetermined strokes of the piston 102.

It is also apparent that therethod of forcing spherical pellets through an orice to obtainth'e'de'sired time delay can be utilized in applications"whereincentrifugal forceV is not available; For example, a `desired delayed'unshorting may be accomplished "withthe" forcejdriving the pistonas the sole means of removing the pellets from the cylinder in such non-spin Vprojectile as"boinbs', rock-v ets, torpedoes, or mortars if'Y gravity or other'means is utilized to continually clear the ejectedpelletsfrom in front of the orifice. It is also apparent that other than spring means may be utilized to`` provide the unidirectional force to eject the pellets from the cylinder, e.g;,k

gravity, expanding gases, compressedain' or a crankshaft on a gas or electric motor. K

Iclaim: j

1. A delay arming device fora rotatin'grartille'ry projectile containing an electrically#operateddetonating squib" uniformly spherical pellets of` substantially uniform sfzeV y and smaller than said orifices arranged within-'said axial recess for preventing movement of and maintaining said piston means in spaced relation with respect to' said rupturable means, centrifugally-operated means having a valve portion provided with an apertureandfarranged within said cylindrical aperture, and resilient means operatively connected to and normally maintaining said centrifugally-operated means in a positionin which said portain maintainsV said pellets in said axial recess against any force of set-back, saidocentrifugally-operated means being rotated, only in response Vtowcentrifugal force sui-V cient to overcome the effect of saidresilient '.ineans, to ak position in which the aperture therein is aligned w`th said orifices for permitting said piston-meansand centrifugal force to expel said pellets at a predetermined rate from said axial recess into said reservoir whereby breaking of said rupturable means to unshort saidelectrical circuit is delayed until a predetermined'number of pellets have been expelled into said reservoir.

2; A vdelay arming device for a rotating artillery projectile comprising 'Yan --electrically-operated detonating squib, a centrfugally-operated gate member carrying said squib and an-unshortingipin and" adapted to move said squib to an armed position `and'said pin to an unshorting position, a Yfixed member having a taut shortcircuiting wirejarrang'ed in the path of said pin'and connected to said squib' and adapted to be' broken by said pin upon movementthereofl to said unshorting position to unshort said squib, an insulating body having an axial recess, a reservoirfa' cylindrical aperture farranged'ral dially between said-recess and said reservoir,'and aligned radial orifices connecting said axial recess and cylindrical aperture'and'said cylindrical aperture and'reser- Voir;rupturablevmeanspositioned over'said axial yrecess for normally maintaining a short circuit across the 'electrical circuit forsaid squib, piston means having a portion thereof normally in engagement with said gate me'rnber for holding -saidfgate- -member ina position'in which. said squib is unarmed and'adapted to be movedk within Y said axial recess,` spring-means for moving saidpiston means, a multiplicityof Vuniformly/'spherical 'pellets of uniform size and smaller than'said orificesarranged within said axial recess for preventing movement of and maintaining said piston in spaced relation with respect to said rupturablemeans, centrifugally-operated means-having a valve portion provided with an aperture and arranged within said 'cylindrical aperture, and resilient means operativelyconnected to and `normally maintaining` said centrifugally-operated means in a positioniin which said valve Yportion maintains said "pellets in'said axial recesslagainst anyforce 'of setback, said centrifugally-operated meansbeing rotated, only in response to centrifugal force suliicient to overcome the elect of said resilient means,-toa position in which the apertureV therein is aligned with said` orifices for permitting said piston means and centrifugal force to expel said pellets at a predeternriined` rate from said--axial recess into said reservoir wherebyfdisengagementofsaid portion'of said piston'means from said gate member to'permit said squib to be moved to an armed positionand said pin'tounshort said squib'is delayed` until' afpredetermined number of pellets have been expelled `into said'reservoir-and the breaking of said rupturable means to unshort said electrical circuit is delayed until Aan additionalV predetermined numberjofV pellets have beenrcxpelled into said reservoir. A v j p Y v Y References Citedlinthefile of this patent t Y- UNITED STATES PATENTS Y VZlegenfuss Q luly9, 1907 2,395,782Y Good Feb. 26, 1946' 2,458,470 Ilafstad i Jan. 4, 19,4

v y FoRErGN PATENTS Y f "107,411 VSwitzerland` `r Nov; l, 1924 '224,241 YGreat Britain`. Aug. 6, 1925 

